Many products currently marketed and sold to consumers are designed for limited use. These products are usually associated with a single event, a restricted time period or restricted access. There are many reasons for the need of single use or limited use products.
An example of a single use product is a disposable syringe. Instrument contamination and cross infection between patients is an ever present concern if the syringe is inadvertently reused. It is a particular concern in some countries where repeated use of instruments is known to transmit serious diseases such as HIV and hepatitis. Medical and ophthalmic devices that must be sterilized such as scalpels or tonometers (for the measurement of a patient's intraocular pressure) and body piercing and tattooing instruments used on multiple clients also give cause for concern. Needles used in acupuncture offer another example. Decontamination procedures or employment of single-use devices are methods used to control cross infection, but they rely on personnel awareness, willingness to follow protocol, monitoring and documentation.
The limited use type of product is usually associated with goods that should be used for a restricted time period. One example of this type of product is “daily wear” or disposable contact lenses. Contact lenses for refractive correction or cosmetic purposes require suitable wear and care regimes in order to maintain good eye health. Non-compliance on the part of the patient, either through choice or due to lack of education, can injure the eye. Frequent replacement lenses are sometimes worn for longer than recommended or they may be stored or cleaned inappropriately.
Other examples of limited use products that have a shelf life after which they should not be used because of a risk of infection or a decrease in effectiveness are cosmetic products, personal hygiene products such as electric toothbrush heads, and home diagnostic kits such as pregnancy tests and ovulation prediction tests. For example, it has been found that cosmetic applicators can harbor bacteria that can infect the eye and should be disposed of prior to their expiration to prevent eye infections.
Many products currently marketed and sold to consumers are supplied prepackaged where the packaging is intended to preserve the freshness of the product such as food or beverages or in the case of medication, the potency of the content within the packaging. These products are usually associated with a single event, i.e., the contents remain fresh or potent until the packaging is opened by the consumer; however, the freshness or quality of the contents may decrease over time.
An example of the importance of preservation of a packaged product is a cold tablet or a food item. Medicinal potency or food spoilage and the expense related to these issues are important to both consumers and manufacturers. Pharmaceuticals, food stuff, and similar items are commonly packaged in sealed plastic containers.
Gas, such as oxygen, permeation through the plastic material of the container negatively affects the freshness or quality of the contents of many packaged products. In the case of pharmaceuticals, oxygen absorption decreases potency. In the case of food products, oxygen absorption into the packaged food makes the food taste stale.
Products may have different intended uses and may have different times after which the product should no longer be used based on the intended use. For example, a single medical device could have many different use protocols. Depending on the use protocol, the medical device should be changed after a different period of time. For example, a catheter could be used in one way where it should be changed after 72 hours but when used another way would not need to be changed until 96 or 168 hours. Medications could also have a different shelf life based on different uses. For example, maximum potency might be required for a certain use while a decline in potency would be acceptable for an alternate use. Foods could similarly have a different shelf life based on their intended use. The same food product might be deemed acceptable for consumption by a pet longer than it would be deemed acceptable for consumption by a human.